An ambient light sensor may be used to adjust the backlighting of the display in many computation and communication devices, such as smart phones, laptop computers, tablets, and the like. Several factors may affect the performance of an ambient light sensor. For example, when the ambient (available) light is provided by a light source powered by alternating current (ac), the power lines exhibit varying light intensity over time according to a phenomenon referred to as ac ripple or ac flicker. This flicker may affect performance of an ambient light sensor. As another example, when the ambient light sensor is disposed under a glass screen of a device, a smudge on the screen caused by a finger print may also affect performance.